The Internet of Things (IoT) is a network or physical objects or “things” embedded with electronics, software, sensors and network connectivity that enable these devices to collect and exchange data. The IoT is expected to explode in the coming years as the hardware and software embedded in these objects and things become smaller and cheaper. A critical component of IoT devices is the transceiver which must be small in physical size, low cost and consume a relatively small amount of power due to the availability of a small battery or alternatively no battery where the device is solely powered by an energy harvester.
Ultra low power (ULP) transceivers underpin short-range communications for wireless internet-of-things (IoT) applications. Their system lifetime, however, is extremely limited by the transceiver power consumption and available battery technology. On the other hand, energy harvesting technologies typically deliver supply voltages that are much lower than the standard supply voltage of CMOS circuits; e.g., on-chip solar cells can supply only 200-800 mV. Although boost converters can bring the level up to the required ˜1 V, their poor efficiency (<80%) wastes most of the harvested energy. Consequently, RF oscillators, as one of the transceiver's most power hungry circuit blocks, must be very power efficient and preferably operate directly at the energy harvester output.
There is thus a need for an RF oscillator suitable for use with ultra low power transceivers that addresses the aforementioned constraints. Such an RF oscillator (1) exhibits ultra low power consumption, (2) operates at ultra low voltage, (3) is small in physical size, (4) is manufacturable and at low cost and (5) does not sacrifice phase purity.